The 'Life of Pi' tiger was 14% real tigers, says visual effects supervisor Bill Westenhofer, who spent some time with them — and who worked on the other 86%.

For director Ang Lee's "Life of Pi," the story of a spiritual Indian boy stranded at sea with a tiger, Oscar-winning visual effects supervisor Bill Westenhofer, who is nominated for this year's Oscars, started with shots of actor Suraj Sharma alone on a lifeboat in a water tank against a blue screen. Working with 1,200 visual effects artists at several companies, he transformed this footage into the character of Pi Patel and a Bengal tiger on a vast, changeable sea. Rhythm & Hues, where Westenhofer works, conjured up most of the animals, seas and skies; other effects companies tackled everything from creating storm sequences and a sinking ship to making Sharma skinnier and Pondicherry, India, look like the 1970s.

So how many of the shots of the tiger are digital?

Only 14% of the shots were real tigers; the rest were digital. The side effect of making a digital tiger is that you get to spend eight weeks with real tigers. It's the most arresting animal you've ever seen. Everything about the way they look, their eyes, the concentric rings. When they look at you, it freezes you in your tracks. It's fun doing this business and it's rewarding making films, but there are experiences that you get that are what you really treasure.

It took about a year to build the tiger. You have a version of the model that you can push and pull in the computer around the shape until it looks right. And then there's an artist who lays in all the muscles and figures out when the arms move around, how they fire and how the skin folds and moves. And then someone else lays in the hair, and there are 10 million hairs put on the tiger, and she's got to paint in the colors and the way it wrinkles and folds. So you work on a version, you compare it to the real thing, and you go month after month until it looks right.

What were the most challenging scenes?

The hardest were when the tiger was in water and especially in the storm, when the boat's splashing around. The water work and having to have water interact with hair and vice versa was, from a science standpoint, this cyclic pipeline of each affects the other. And the tiger's being done in one software package, the water's being done with another. We've got to get them all to talk to each other and to interact. They were by far the longest shots in production and the hardest that we did.

We do this thing called "previs," and it's almost like video game-ish graphics. You can show Suraj: Here's what the shot's going to look like. That's where the tiger's going to be. If that wasn't enough, you could use eyeline pulls. An eyeline pull could be getting a really long pole and putting a couple tennis balls on the end. And while the scene is being shot, you'll move the tennis ball through the frame so that the actor has something to look at.

Sometimes you make what are called "stuffies." Think of a stuffed animal that's the size of the tiger. Or quite often, my animation director — his name is Erik De Boer — would put on a blue leotard, hop on the boat and play the tiger for Suraj. When Suraj is doing things like jabbing the stick at the tiger, Erik would swat it and give the physical reactions so that the response is genuine.

What went into creating the seas and skies?

The oceans and the skies carried a lot of the emotional message of various sequences in the film. Ang is great. He's not going to come and tell you, "I want 30% cloud cover." He'll come and say, "I want an operatic sky," or "I want an enigmatic or a pensive look." And then it was up to us to figure out what that means, which was great.

Ang came to Rhythm & Hues right after shooting was done, and he addressed the crew. He concluded with, "I want to make art with you." That resonated with the crew, and that's how all of us approached things. It was an awesome challenge and very rewarding to be able to supply that.